|  | Stigmas 3; achenes three-sided,
        occasionally terete, though their shape may be concealed by flattened
        perigynia; NOT [Stigmas 2; achenes lenticular] | 
      |  | Spikes 2 or more per culm, terminal and
        lateral; spike bracts present on lateral spikes (except in Section Phyllostachyae),
        lowest bract usually evident, often conspicuous.  NOT [Spikes 1 per
        culm, terminal; spikes bracts absent] | 
      |  | Lower pistillate scales not bract-like or
        leaf-like but similar in size and shape to individual perigynia (up to
        twice as long as perigynia in C. magellanica ssp. irrigua]; NOT
        [Lower pistillate scales resembling green, leaf-like bracts much longer
        and wider than individual perigynia.  Section Phyllostachyae] | 
      |  | Perigynia sparsely to densely pubescent
        or puberulent (in C. pedunculata pubescence represented by very
        short hairs scattered near tip; in some species of Sect. Acrocystis,
        perigynia may be glabrous or virtually hairless, but all members of this
        group have convexly 3-sided to terete achenes with tight-fitting
        perigynia and a stipe-like base about equal to beak in length). 
        NOT [perigynia glabrous (i.e. lacking a pubescence)] | 
      |  | Perigynia usually less than 5 mm long but
        if longer, beak distinctly shorter than perigynium body; pubescence
        various. NOT [perigynia 5-7 mm long with beak as long as or longer than
        perigynium body; pubescence on the perigynia dense, stiff and pointing
        toward tip] | 
      |  | Achenes convexly 3-sided to terete;
        perigynia tightly enclosing achenes and convexly 3-sided to terete,
        sparsely pubescent, (rarely glabrous in C. deflexa and C.
        rossii, pubescent only on ribs in C. tonsa); stipe-like base
        about equal to beak in length; pistillate spike bracts sheathless. 
        Section Acrocystis. NOT [Achenes with +/- flat sides; perigynia
        loosely fitting achene and variously shaped in cross-section, densely to
        sparsely pubescent (faintly puberulent with very short hairs scattered
        near tip in C. pedunculata); pistillate spike bracts sheathing or
        sheathless] | 
      |  | All pistillate spikes cauline, i.e.
        attached near top of regular, elongate culms and born at or above level
        of leaf tips. NOT [Some or all pistillate spikes basal, i.e. attached
        near base of plant and borne among leaf bases] | 
      |  | Staminate spike 10-20 mm long,
        conspicuous above pistillate spikes; plants in dense tufts with copious
        fibers on crown; leaves of vegetative shoots stiff, erect and nearly as
        tall as inflorescence; plants of dry prairies. NOT [Staminate spike 3-10
        mm long, inconspicuous among pistillate spikes; other features not as
        above] |